What do the following two equations represent? $-5x+5y = 4$ $-25x-25y = 4$
Explanation: Putting the first equation in $y = mx + b$ form gives: $-5x+5y = 4$ $5y = 5x+4$ $y = 1x + \dfrac{4}{5}$ Putting the second equation in $y = mx + b$ form gives: $-25x-25y = 4$ $-25y = 25x+4$ $y = -1x - \dfrac{4}{25}$ The slopes are negative inverses of each other, so the lines are perpendicular.